Time warning arrangement for telephone systems



vJan. 7, 1.947 H. E. GORDON VTIM WARNING ARRANGEMENT FOR TELEPHONE SYSTEMS Fil'ed may 21, 1945 Patented Jan. 7, 1947 TIME WARNING ARRANGEMENTFOR TELEPHONE srsTEMs Harry E. Gordon, Rochester, -N. Y., assignor to 1 Rochester Telephone Corporation, Rochester, N. Y., a corporation of New York Application May 21, 194,3, Serial No. 487,947

2 Claims.

'.up telephone equipment including cord circuits and other'connecting links, vthereby necessitating an increased amount yof such equipment With increased service cost to the telephone operating company.

It has been found that nearly all of these connections of excessive duration arise from the fact that the subscribers involved therein are thoughtless as to the passing of time and that if they are given time Warnings vthey Will gladly cooperate.

Prior to this invention it has been proposed in the case of each individual telephone connection to start measuring time as soon as the called party to the connection answers, and then to give a warning signal at the conclusion of a predetermined interval. Such an arrangement, while effective, is so complicated that it has not gone into extensive commercial use.

In accordance With the main feature of the present invention, it is proposed to apply an audible signal at regular predetermined intervals to each cord circuit or other connecting links of a telephone system, irrespective of Whether these links are being used in telephone connections or whether they are idle, and without regard to the starting time of a connection.

Another feature of the invention relates to the character of the Warning tone current and the manner of introducing it into the link circuits so that cross-talk eiects Will be substantially avoided and Warning tones of substantial uniform sound level are reproduced at the substation of both short and long telephone lines.

A further feature of the invention relates to arbitrarily dividing the link circuits of a telephone system into groups and applying the Warning signals to these groups in succession or in staggered relation so that the load on the signalling equipment can be uniformly distributed.

The single figure of the drawing ydiagrammatically represents a portion of a telephone system incorporating therein the automatic time Warning arrangement of the present invention.

While the invention is herein disclosed in connection with the cord circuits of afmanual tele` phone system, it will be understood that it can be applied with equal usefulness to certain of the link circuits of an automatic telephone system. In this disclosure only a calling subscribers line A and a called subscribers line B of all of the lines of the system, are shown for interconnection by any one of several link circuits such as the cord circuits 5. These cord circuits may be of the usual type and therefore only the talking conductors thereof are illustrated, it being understood that the conventional equipment associate'd with these cord circuits has been omitted for simplicity in description.

ln practicing the present invention, it is propoaed t0 apply to :the various cord or link circuits of a telephone system, whether or not these circuits are in use, Warning signals preferably audible in character. Such Warning signals are applied periodically to all cord circuits of a group, at the end of a predetermined time interval, Without regard to the time that rany given cord circuit was Viirst taken yfor use. Thus, it may happen that the subscribers on a telephone connection will vhear the Warning signal shortly after they first engage in conversation, but all of the subscribers soon learn to disregard such early Warnings.

The signal applied to the subscribers line is preferably of one thousand cycle frequency current since current of that frequency is transmitted over long telephone lines with negligible attenuation effects. Thus, the warning tone reproyduced atv the substation of a long telephone line Will not differ materially in sound level from the warning tone reproduced at the substation of a short telephone line. 4Also the human ear is most sensitive to a frequency of one thousand cycles per second, -Which frequency provides a per signal that is readily distinguished from other signalling tones, such as ringing tone and busy tone, commonly used in the system. The source of this audlble tone signal is preferably a vacuum tube oscillator 16 `of Well-known construction and to insure that the tone is of the desired audible level, the output Yofthe oscillator is introduced into an audio amplifier v'l of any Well-known type. The output of the ampliflien in turn, is connected in series with certain of the windings of a repeating coil provided with the windings 9, Iii, H and i2 of Well-known construction although any other source of signalling tone maybe used. This repeating coil cooperates with means to be described to connect the amplier output to the several link circuits.

It has been mentioned that the tone current is applied to the groups of cord or link circuits in succession to distribute the load on the tone signal generator. As herein illustrated, twelve different groups of link or cord circuits are provided and, therefore, a terminal strip I3 with twelve horizontal rows or groups of terminals Ida, I ab, I-'ic and ld are provided, it being understood that each horizontal row of terminals is individual to a group of link circuits. In the present showing, however, only two cord circuits 5 of one group are illustrated, but it will be understood that there are other cord circuits in this group as indicated by the broken conductors. Each group of cord circuits is provided with a group relay it which is periodically energized to apply the tone to the cord circuits thereof as will be further described.

The application of the tone current is-controlled by a twenty-two point stepping switch with brushes SI and S2, all of well-known construction, which switch cooperates with other means to actuate in succession the other group relays (not shown) such as I6, so that the warning signals are applied to the groups of link circuits in sequence. A timer T, common to the system, develops a momentary timing impulse at regularly recurring intervals, such as every fifteen seconds. Preferably, the timer comprises a motor-driven cam which closes the contacts I5 every fifteen seconds.

With this brief description of the equipment involved, it is believed that the invention will best be understood by setting forth how the tone current is applied to the successive groups of cord circuits. When the system is in use, the key il is closed to energize the relays I8 and i9 in an obvious circuit. The relay I8 attracts its armature to extend the 120 volt 60 cycle current source to the terminals of the double outlet receptacle 2B and thence through the plugs 2| and 22 connected to the power leads of the tone oscillator 6 and the amplier l which thereupon continuously develop one thousand cycle tone current at a predetermined level of audibility. Let it be assumed that the stepping switch has its brushes SI and S2 in engagement with their respective #l terminals of the switch bank. Under these conditions, when the contacts I5 of the timer T close, a timing impulse is applied through the armature and front Contact of the relay I9, winding of the relay 23 to ground, so that the relay 23 will energize. When relay 23 energizes, it operates relay I5, from grounded battery, terminal Idd, conductor 24, winding of relay I6, conductor 25, terminal Mc, conductor 2t, switch brush S2, conductor 2l, front Contact and armature of relay 23 to ground. Also when relay 23 energizes, it completes a signalling circuit including the winding I2 of the repeating coil, to one group of cord circuits. This signailing circuit extends from the winding I2 of the repeating coil, conductor 28, lower front contact and armature of relay 23, conductor 29, termina] Ita, conductor 3G, front contacts and armatures of relay I5, conductor 3| with the condenser 32 therein, and the ring conductor of the several link circuits 5 to ground, and also from the repeating coil winding I2, conductor 33, front Contact and armature of relay 23, conductor 34, terminal Ib and conductor 35, to ground. It should be pointed out that conductor 3G is preferably formed into a twisted pair with the dead end conductor 3Ia connected to the tip conductor of the link circuits to obviate undesirable cross-talk effects. It will be understood that if a cord circuit is in use, this tone current will be applied to both the calling and called subscribers line connected thereto. Also, when the relay 23 operates, it energizes the motor magnet MM of the stepping switch, preparatory to advancing the switch brushes SI and S2 to their #2 position. The energizing circuit of the motor magnet extends from grounded battery, heat coil H, winding of the magnet, through a non-inductive resistance NR, front contact and armature of relay 23, to ground.

At the conclusion of the momentary tone impulse, the relay 23 deenergizes and consequently the relay I6 will release to disconnect the tone current from its related group of link circuits. In addition, relay 23, on releasing, causes the motor magnet MM of the switch to deenergize and as a result thereof advances switch brushes SI and S2 to their second position. On the next time impulse, the relay 23 will again be energized and the motor magnet MM of the switch will also be energized in readiness to move its switch brushes to their third position. However, with these brushes in their second position, the warning tone current will be applied to the second group of link circuits. At the conclusion of this second time impulse, the switch brushes SI and S2 are advanced to their third position. In each oi the twelve dierent positions of the switch brush, the warning tone current is applied to the link circuits of a particular one of the twelve groups of these circuits.

When, however, the stepping switch. has advanced its brushes SI and S2 to their thirteenth position, this switch will automatically step these brushes back into their #l position. This is effected in a circuit extending from grounded battery, winding of the heat coil and winding of the motor magnet, its armature and back contact, through the terminals #13 to 22 inclusive which are multiple together, switch brush SI to ground. The magnet MM self-interrupts this circuit to step the switch brushes SI and S2 forward to their #l position. It should be pointed out that, since the timer T develops an impulse every fteen seconds and since the stepping switch effects the rst twelve directive steps of its brushes in response to these impulses and then automatically steps these brushes through the remainder of the cycle of operation to their #l position, this cycle is completed in approximately twelve times fteen seconds, totaling onehundred-eighty seconds or three minutes. Thus, as the stepping switch continuously steps its brushes SI and S2 through a complete cycle every three minutes, the warning tone will, therefore, be applied every three minutes to the respective groups of link circuits in succession.

The present invention, besides tending to shorten telephone conversations, can be slightly modified to effect more uniform traffic distribution during a given period. Trac studies have shown that in the average telephone system, the number of telephone calls increases from early morning to mid-morning when there is a high number or traiic peak. From this high peak, the number of calls decreases to a more uniform load until late afternoon and again in early evening when lesser trafiic peaks occur. It need not be pointed out that greater efciency in the services of the operators and in the use of equipment result if the traffic load is maintained more uniform. Thus, if some of the calls normally originating during the mentioned peak periods could be postponed until such times as the traic 5 load is usually lighter, the desired uniformity could bemore nearly approximated. This result may be effected by changing the frequency of the warning signals during different periods of the day, depending on the incidence of the traffic peaks. For example, during the peak periods, the warning signals may be transmitted every three minutes or oftener, whereas, during lighter traffic periods, the warning signals may be sent out at the end of longer intervals, for example, after the lapse of six minutes. The telephone subscribers can then be instructed that during certain periods of the day they'can continue their telephone connection for longer periods as evidenced4 by the longer time between warning signais. Subscribers are prompt to respond to such conditions, so that many of the purely social" calls will wait until the so-called lighter traflic periods when the warning signals occur less frequently. A marked improvement in load distribution will thereby be achieved. It will be understood that when it is desired to transmit the warning signals at six-minute intervals, the timer T will be arranged to close contacts I5 every thirty seconds instead of every fifteen` seconds. Otherwise the system operates as above described. Although a vacuum tube oscillator and amplifier have been disclosed as the source of tone current, other devices may be used for this purpose. Also,

the frequency of the tone current may vary widely from one thousand cycles. While the tone current is herein applied to the link circuits through a twisted pair of conductors 3l, 3 la, one of which includes a .02 mf. capacitor therein, other arrangements may be substituted therefore, Without departing from the spirit of the invention.

What I claim is:

1. In a telephone system, a plurality of telephone lines, means including groups of link circuits for interconnecting said telephone lines, a source of signalling current of audible frequency, and means for applying .said signalling current to said groups of link circuits and to telephone lines connected thereto, in sequence at regularly recurring intervals without regard to whether or -not said circuits are in use.

HARRY E. GORDON. 

